DE 37 32 351 A1 (U.S. Pat. No. 4,889,555) already describes a process for producing binderless briquettes for charging a smelting operation, comprising metallic-iron-containing fine-grained steel plant dusts which are heated up and, while in the hot state, turned into briquettes on a roller briquetting press and are subsequently cooled. To avoid reoxidation, this is intended to take place under an inert atmosphere.
Disadvantageously, a considerable amount of energy is necessary here for heating up to the briquetting temperature in excess of 500°.
DE 44 16 699 A1 describes a process for utilizing metallic residual material, in particular chip material, in smelting furnaces, in which the small-sized chip material to be recycled is pressed together with slag- and/or fuel-forming dust, preferably dust containing SiO2 from filter systems, with up to 15% by weight, preferably 5 to 10% by weight, of dust being admixed with the amount of material to be pressed. In the case of this process, the amount of metal dusts is greatly restricted.
Attempts to press metal dusts that occur for example in grinding processes into briquettes without further additives failed as a result of the inadequate dimensional stability of the pressed product. Even slight impact or other force effects on a briquette body produced purely from dusts caused it to break up. The alternative of adding adhesives is laborious and also implies that, when the dusts are put to further use, the adhesives must first be removed again by heating.
In times of constantly increasing raw material prices, there is an urgent need to recycle in particular expensive metals and metal alloys that are contained in waste materials occurring in waste from machining operations, in particular grinding. However, a precondition for this is solid shaping, allowing such waste to be stored and transported without the risk of it breaking up. The same also applies correspondingly to the dusts originating from metal-processing processes that collect in filters.